Automatic circulating bleeding system for hydraulic brakes



April 25,1950

INVENTOR. San 5 SOS/NEAL I I J S. SCHNELL AUTOMATIC CIRCULATING BLEEDING SYSTEM FOR HYDRAULIC BRAKES Filed June 12, 1944 Patented Apr. 25, 1 950 Steve SchnelLKi'rkwood, Mo}, assignor to Wagner Electric Corporation, St. Louis, Mo., a corporat tion of Delaware en i a z-li el? 4. S ia N 53 85 '7 Claims.

This invention relates to hydraulic brake actuating systems for use on cranes, hoi'sts,.derricks, and selfpropelled vehicles andin its'more specific aspect-s'isdirected to a system in which the liquid is circulated through the several devices of thebrake system in order to effectively and efiiciently bleed any entrapped air from' the hydraulic pressurefluid portion of the system.

The object of theinvention is to provide in a hydraulically-operated brake, a valve sy'stem arranged between the master cylinder, brake cylinder, and fluid reservoir, which provides for a substantiallyclosed fluid systemin Whichsaid fluid flows in one direction only to enable en'- trapped air to be bled-fromthe brake cylinderl Afurther object of the invention is to'provide a hydraulically-operated brake in which there is a substantiallyclosed pressure fluid system havinga valve therein that enables one portion of the system to be segregated from, another portion'of the system such that any entrapped air in the second mentioned portion is bled from the brake cylinder to the fluid reservoir and any fluid in the second portion is also returned to the fluid reservoir.

Other and-further objects of the invention will occur to those skilled inthe arts to which thls application pertains as the description' proceeds, which, taken in connection with the aceemp pa ing drawing, sets forth apreferred embodiment of the inventionbut such disclosure is not'ito be construed as a limitation of the invention which is limited only by the appended claims and any and all modifications, alterations and variations of structure coming within thes'pirit and scope thereof are deemedto be included herein.

In the drawing; t

.Figure .1 shows a schematic layoutof the invention with parts in section to show details of construction.

The hydraulic brake arts have devised various means and mechanisms for the removal of entrapped air in brake cylinders, all-cf which have required thepersonal attention of operators and service attendantsto gain or have access to the brake cylinder itself in order to open thebleeder valve and release the entrapped air. The entrapped air whenpresent in the system is an extremely troublesome factor contributing roan unreliable operation of the brakes and can only be removed from known prior art devices at considerable inconvenience and: expense in; time and labor. Also, when the bleeder valves heretore s d nrco n i iwi h h r liemekezs tems had been opened, it had been necessary for the attendant toprovide himself with a vessel of onevariety or another-Ito catch any fluid that was drained from the pressure system and then restore it to a reservoir associated with the master cylinder; This inventionprovides a convenient means and mechanism for eliminating the manuaiopenmg and closing of a bleeder valve located on the brake cylinder and subjects the bleeder valve to the control of the operator by manipulating theImaster cylinder in a predeterminedlmanner, thereby providing for the circulation of liquid through the brake system and simultaneously removing any entrapped air therefrom. In such installations as traveling cranes, portable hQiStsandLderrickS, self-prop'elled'vehicles, and so forth, where the brake is located; at aconsiderable distance from the master cylinder device usually located at the operatorsstation, he can so manipulate his master cylinder that. entrapped air will be bled from the brake cylinderandthus maintain a solid line of liquidlbetweenthe master cylinder and the brake cylinder to provide for a positive and more efiicientoperation of the brake.

The above objects and advantages are achieved in thestructur'e set forth in the accompanying drawing in which I is a reservoir preferably 10- cated at some elevated point having a valve housing 2 secured thereto by rneans of hollow or bored screw elements 3; 3'extending through the bottorn'wallof the reservoir and threaded into suitable bosses '4' 4a in the valve housing. One of these bosses, 4, has an aperture formed therein at the lower end of which is threaded a conduit 5"thatleadsto a reservoir (not shown) located 1 in' master. cylinder device 6 Whose internal construction may be similar to that illustratedin United States Patent No. 1,758,671 to Loughead' et,al., dated May 13, 1930, for Pressuielinechanis'm for brake'systems. .A foot peda1 .1 is pivotally mounted on the device 6 by means of spindle 8" such that it may actuate a piston device (not shown) located within the mastercylinder device ii'dn order to generate pressure in'ithe fluid'system. Theppressure fluid is'exhausted from themaster cylinder device 6' through conduit 5 whichis threaded intoan other bossv warm d invhofu sing' 2. Another boss I isfQrmedon anether'part of the housing? to' which conduit 1-2 1 is I connected leading to the intake side-of brake cylinder t3 and conduit IA leadsfromthesexhaust side'of brakefoylinder i3 andis threaded intoa bossed end of another no i i bith va v hqu 'i .2

Brake cylinder i3 forms a' part of the brake assembly shown in the drawings in which 52 and 53 are pivoted brake shoes on which suitable friction elements are mounted. One end of brake cylinder I3 is pivotally associated with member 53 and its opposite end is pivotally associated with member 52. Spring is connected between brake shoes 52 and 53 to release them from engagement with the cooperating brake drum when pressure fluid is released from brake cylinder l3.

Valve housing 2 has a shell portion |5 threaded into said housing, one end of which is bossed, bored, and threaded to receive conduit I4 as previously described and pressure fluid is led through said bore in the end of shell l5 thence through suitable passageways subsequently described to and through the second bored screw element 3 threaded into the boss 4a on housing 2 and exhausts any fluid and air contained in conduit l4 and brake cylinder I3 into the reservoir or sump Valve housing 2 and shell 15 are concentrically bored to receive a piston I6 having a sealing cup element arranged on the end l8 thereof and providing with the bore in housing 2, a chamber Hi. Pressure fluid generated by the master cylinder device 6 exhausts into the chamber I9 and urges piston l3 and sealing cup I! thereon to the left as viewed in the drawing. After pressure has been bluilt up to a predetermined value, it exhausts through duct 20 opening a normally closed intake valve 2| for motor l3 against the pressure or tension of spring 22. A cap and plug element 23 is threaded into the boss H and applies tension to said spring to urge the valve to closed position. A suitable gasket may be arranged between the cap element 23 and the boss H in order to prevent leakage of pressure fluid. When the predetermined pressure has been built up, valve 2| is opened, allowing pressure fluid to be admitted to conduit l2 and thence conducted to brake cylinder l3 to operate the same. Pressure fluid continues to flow until the pressure in conduit l2 equals the pressure in chamber |9 whereupon valve 2| recloses.

Pressure fluid is also appliable to the opposite end of the valve housing and shell I5 has arranged therein a piston 24 provided with a sealing cup 25. The piston 24 is turned down and slotted as at 25 and forms a chamber 2'5 which receives pressure fluid coming from conduit I4, pressure fluid being conducted through said slot 26. The web 28 of the piston has an aperture 29 provided therein that connects the chambers 39 and 3|. The piston.24 normally rests against the end of shell 15 as shown in the drawing, be

ing urged into that position by the action of spring 38 later described.

Piston I6 is or" a longitudinally extended variety and its left end receives the exhaust Valve element 32 that engages the exhaust valve seat 33 formed on the end of piston 24. The chamber 34 connects, by means of duct 35, with previously described hollow screw element 3 to exhaust intothe reservoir fluid passing passage 41 constituting the space closed by the valve element 32 engaging the seat 33.

Piston It has a stud 36 arranged in the end thereof extending through valve 32 and has a threaded reduced end extending through the web 28 and piston 24 and is rigidly secured thereto by means of a nut and washer combination 31. A spring 38 is arranged within piston l6 and engages the end of stud 36 and at its opposite end it engages with a plug element 39 fitting in a counterbore 4| concentric with chamber l9. Concentrically disposed within the spring 38 is a sleeve 49, one end of which is fixed to the plug 39. Spring 39 is a relatively strong spring and urges the piston 24 through stud 36 into engagement with the left end of shell l5.

Plug 39 closes one end of the counterbore 4| and has a slot 42 formed therein connecting the chamber formed by counterbore 4| with the chamber l9. The counterbore is further counterbored, extending through to the duct 4 formed in the valve housing and the larger diameter portion of the counterbore has a sealing cup 43 therein arranged about a flanged sleeve element 44. The sealing cup 43 forms a valve seat for valve'45 and spring 46, which is of a very small gauge, fits about a bossed end of plug 39, and serves to hold valve 45 centrally disposed with respect to the valve seat formed on sealing cup 43. Valve 45 permits fluid to flow from reservoir to chamber I9 but prevents a reverse flow of fluid from chamber l9 to reservoir The operation of this device depends upon intermittent application of the master cylinder device 6 producing pressure within chamber l9 and opening valve 2| after the pressure has increased to a predetermined value to thereby admit pressure fluid to the brake cylinder i3. The building up of pressure in chamber I9 urges piston l5 to the left and closes the passageway 41, thereby preventing flow of any fluid in conduit I4, chambers 39, 3| and 34 to the reservoir or sump Upon the release or cessation of operation of the master cylinder device 5, pressure fluid will escape from chamber I9 back to the master cylinder device 6 through conduit 9. Retraction of the piston in the master cylinder 6 under the influence of the spring therein normally draws back fluid by suction and after the uncovering of the compensating port, gravitational action balances the fluid columns. Pressure fluid from brake cylinder It will be prevented from flowing back to the master cylinder device because valve 2| will close as soon as the pressure on one side thereof is equal to or higher than the pressure in chamber I9 and will remain closed as long as this condition exists. Simultaneously with the release of pressure fluid from chamber I9, pressure is still present in space 21 by reason of having been put there by the action of master cylinder 6, spring 5| in retracting the brake shoes, and the reduction of pressure in chamber l9, all of which combine to maintain pressure in said chamber 2?, which pressure will urge pistons 24 and IE to the right until such time as face 48 on stud 36 engages with the end 49 on sleeve 49. Spring 5| associated with the brake assembly is of a strength suflicient to move pistons l5 and 24 in the cylinder in housing 2 against'the action of spring 38. Continued motion of piston l6 by reason of the aforesaid pressure will produce relative motion between piston 24 and piston it on stud 36 to thereby open the valve passageway 4'! and permit pressure fluid to flow into chamber 34 and thence into reservoir I through duct 35.

I On initial installation of the apparatus, or at any other time when it may be thought advisable to have assurance that the system is free of entrapped air, the brake pedal may be actuated in brake applying direction and released several times whereby a substantial quantity of fluid will be moved through the system to the reservoir and thus assure that all entrapped air is carried out of the system.

After release of pressure on the fiuid rin chain as land urin'g thefirestol'ation'" of the piston te the positid iindicated in thevfigure under'th'e influence of spring 38, a-partialvacuum may be cre'atedl'in'chamber l9, Thisivacuum causes the opening l of valve -'4'5,.:al1owing:liquid to flow from conduit 4 and reservoir 1 into chamber l9 until it is completely filled whereupon when the same pressure will exist-on one side'of the valve 45 as on the other, it will close; By this means the system below valve=2:l' is alwa'ys maintained' full and ready for the next operation: Pressure in chamber 19 will actto firmly seat valve 45 toprevent pressure fluid from flowinginto reservoir I from saidchamber; If i. any vacuum is produced in the brake cylinder or chambers 21,39, 31, and tllor conduits I;2 and l4 connected therewith; they will be fllledby-fluid flowing through duct 35 from reservoir I through the aperturedjscrew ,3 therebymaintaining the other side of the brake system filled with liquid. Liquid circulated by the above device iprevent'shea'ting-and a re-use of any heated liquid that may be in the system.

Having fully describedmy invention, what I claim as new and desire to secure by Letters Patent of the United States is:

1. In a hydraulic brake system; a master cylinder; a. brake cylinder; an" elevated liquid reservoir; a control element; a first conduit connecting said reservoir and said master cylinder; 'a'second conduit connecting said controlelement and master cylinder; a third conduit connecting said'controlelement andsaid brake cylinder; a fourth conduit connecting said brake cylinder and said reservoir; a first valve in the' contr'ol element arranged in said fourth conduit; means to operate said valve controlled by said master cylinder; a second valve in said control element arranged in said third conduit; said first mentioned valve when closed by said master cylinder preventing flow of pressure fluid into said reservoir through said fourth conduit; said second valve holding pressure fluid in said brake cylinder after said master cylinder is operated to thereby operate said brake cylinder, and when pressure is relieved on said means the pressure fluid held by said second valve will open said first valve to exhaust liquid and entrapped air into said reservoir.

2. In a hydraulic brake system; a fluid reservoir, a master cylinder, and a brake assembly; conduit means to serially connect each of said devices; a control element rigidly connected to said fluid reservoir, said control element containing ducts included in said means to serially connect said devices, said control element comprising a pair of valves including a normally closed inlet valve for said brake cylinder and a normally open exhaust valve for said brake cylinder; said exhaust valve comprising a piston device on one end of which said exhaust valve is mounted seatable on another piston device axially aligned with said first mentioned piston; said exhaust valve closable by pressure fluid developed in said master cylinder and exhausted into said control element and acting against said first mentioned piston to close said exhaust valve; said inlet valve openable after pressure fluid in said control element achieves a predetermined value to operate said brake cylinder; said exhaust valve opening when pressure is relieved against said piston while said master cylinder is inoperative; and pressure fluid in said brake cylinder opening said exhaust valve by urging said first mentioned piston in the opposite direction from which it was first moved to thereby exhaust fluid in said brake cylinder to said fluid reservoir.

3; In a'icontrol element ror :a hydr" mic b'rake; a longitudinally extended housing; 'a l'ongitiidinally extended first ipisto'n 1 reciprocablyimounted in said housing; a-isecdndpis'ton mountedin said housing and connected tosaid first' piston means to permit less relative movement of one piston with respect to the other; :a valve arranged between said pistons closable' upon relative movementor said pistons; a second valve associated with said housingandopenable after a predetermined pressure is present in saidhousingacting against said'valve; a. third'valvelinsaid'housing to permit fluid to enter said housing from said' reservoir when a vacuumis-producedztherein following any excess movement of said pistons relative to each other; and resilient meansurging saidsec ond piston into engagement with one end of=.said housing tomaintain said exhaust valve in open condition.

4. In a control element for a hydraulic-brake; a longitudinally extended vhousing having a fcylinderbore therein; a first pistonelement in said core; a second piston element'in said boreymea'ns' connecting said pistons for simultaneous-movement and movement relative'to ea'chother; resilient means urging saidisecond' piston into'engagement with the end of said cylinder bore; valve means disposed betweensaid pistons and main-'- tained in a normally open condition by said resilient means; a second valve normally closed arranged in said housing; and a third valve in said housing connectable to afluid reservoir to admit pressure fluid therefrom into said piston when a vacuum is produced 'insaid cylinder bore because of excess'movementof said lfirstpi'sto'n in said cylinder bore.

5. In a hydraulic brake system; a fluid reservoir, a master cylinder, and a brake cylinder serially connected, said reservoir disposed in an elevated position with respect to said brake cylinder and said master cylinder; a control element secured to said housing and including duct means connected to said means serially connecting said devices; said control element including a longitudinally extended housing havin a cylinder bore therein; a first piston in said bore; a second piston in said bore; means connecting said pistons to enable one piston to move relatively axially of the other in said cylinder bore; a normally open valve between said pistons arranged on the exhaust side of said brake cylinder; a normally closed inlet valve fixed in said housing and arranged in the inlet of said brake cylinder, said exhaust valve closable upon relative motion of said pistons by pressure fluid introduced into said cylinder bore from said master cylinder, said inlet valve opening after pressure fluid obtains a predetermined pressure value and thereafter operating said brake cylinder, said inlet valve closing when the pressures on opposite sides thereof are equal; pressure fluid entrapped in said brake cylinder moving both of said pistons upon release of pressure in the cylinder bore when said master cylinder is inoperative; means to arrest the motion of one of said pistons to thereby open said exhaust valve by said entrapped pressure fluid; and valve means controlling a passage between said fluid reservoir and said cylinder bore when vacuum is produced in said cylinder bore; resilient means to urge one of said pistons to their normally inoperative position; said vacuum being produced in said cylinder bore upon return motion of said first piston and fluid from said reservoir filling said cylinder bore by the action of the vacuum therein on saidt'hird valve.

- 6. In a hydraulic brake system; a liquid reservoir, a master cylinder, and a brake cylinder serially connected; said reservoir disposed at a higher elevation than said brake cylinder; conduit means to serially connect said devices; a control element rigidly connected to said reservoir; duct means in said control element connected to said conduit means to serially connect said devices; said control element including a housing having a longitudinally extended cylinder bor therein; a first piston in said bore; a second piston in said bore; means connecting said pistons to enable them to move relatively axially of each other; a valve arranged in one of said pistons and seatable against the other of said pistons and arranged in the exhaust of said brake cylinder; an inlet valve in said housing disposed in the intake to said brake cylinder; resilient means in said bore urging one of said pistons into engagement with the end of said cylinder bore and to normally maintain said exhaust valve in open condition, said master cylinder exhausting into said cylinder bore against said first piston to close the exhaust valve, said inlet valve opening after the pressure in said bore is at a predetermined value and closing when pressure on both sides of said inlet valve is at the same value; pressure fluid in said brake cylinder urging both of said pistons in a direction opposite to the first movement imposed on said first piston; and mean to arrest the motion of said second piston and open said exhaust valve to thereby exhaust fluid from said brake cylinder to said reservoir; and other valve means operable by vacuum developed in said cylinder bore when said longitudinally extended piston is restored to its normal position, said valve closable when the cylinder bore is again filled with fluid derived from said reservoir.

'7. In a hydraulic'brake system, a fluid compressor; a fluid reservoir positioned a substantial distance above the compressor; a fluid motor having an exhaust port and an inlet port; means establishing communication between said exhaust port and said reservoir; a valve in said means; means establishing a fluid pressure line between said compressor and said inlet port; a valve in said last mentioned means to prevent the flow of fluid from said motor to said compressor; means establishin communication between said reservoir and the fluid line connecting the compressor and motor; and a valve in said second means to prevent flow of fluid from said compressor to said reservoir.

STEVE SCHNELL.

REFERENCES CITED The following references are of record in the flle of this patent:

UNITED STATES PATENTS Schnell June 13, 1944 Certificate of Correction Patent No. 2,505,213 April 25, 1950 STEVE SCHNELL It is Hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows:

Column 6, line 6, strike out the word less; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 1'8th day of July, A. D. 1950.

[SEAL] JOE E. DANIELS,

Assistant Gommz'saz'oner of Patents. 

